October 30: LEMON manuals on a temporary server, it is slow and having issues, download the manuals you need! Later in November we will switch back to the fast server.

Engine Backfires

Check for excessively lean air/fuel mixture.
Check for an air intake leak. Idle speed will usually be faster if an intake air leak is present.
Check for leaking air into or out of the exhaust system.
Check for air leakage past valve guides or valves.
Check for ignition timing retarded.
Check for incorrect valve timing.
Check for valves sticking open.